Market

By purchasing this item you can directly exchange ‍ 10 for 1 Neurodes.

—In-Game Description

Neurodes can be purchased directly from the market for ‍ 10. Alternatively, players can purchase their blueprints for ‍ 100, or doing Raid The Law of Retribution Nightmare where the permanent blueprint can be dropped as a mission reward, blueprints are permanent and reusable. (Edit: The Law of Retribution Nightmare raid is no longer available for play until an undisclosed date when Raids have been reworked and re-released).

Gathering Tips

These are based on opinions and may not be true. These should be viewed as advice unless proven undoubtedly true. Check comments for confirmation. Results may vary.
Please note each of the tips below is a subjective average, and may not necessarily represent your experiences.

Plato (Lua) guarantees a spawn of Sentients within the first couple of minutes. This is the most effective way of farming Neurodes, but bring a party, as Sentients do prove difficult.

Orokin Derelict Assassinations (Lephantis) are one of the easiest ways to acquire Neurodes (1-2 average every run), although Derelict Assassination Keys can only be created once every hour. These special derelict keys also require Lephantis Nav Coordinates, which can only be acquired through other Orokin Derelict Missions.

Newer players might find it helpful to search missions in Earth for Neuroptic Masses, the resource container for Neurodes. The chance for enemies to drop Neurodes is very low, making it worth spending time to search for the containers instead.

Sentient fighters spawning on Lua have a relatively high chance of dropping Neurodes (can be accessed upon completing The Second Dream quest).

A widely held misconception among players is that Neurodes are easy to acquire on Orokin Derelict Defense Missions. Not only can this be difficult for some players, but it averages 1 Neurodes every 30 waves. (tested with a Nekros performing Desecrate, may need further testing to confirm).

Another misconception is Orokin Derelict Survival, which does yield more than the defense mission. However it is about 3-4 Neurodes for every 30 minutes, assuming that you have a Nekros performing Desecrate.

Eris survivals and defense (including Dark Sectors) do NOT yield many Neurodes, about 1 for every 20 minutes/waves.

Trivia

The singular form of Neurodes is Neurodes, according to the game.

The descriptions of Neural Sensors and Neurodes were swapped several times, at one point completely reversing what the components clearly were. This was finally reverted in Hotfix 15.16.2 to properly fit their obvious designs.